ShellPkg: Fix 'ifconfig' can't get the address from dhcp in some case

R18201 fix caused ifconfig in shell failed to get the address from dhcp with the
command "ifconfig -s eth0 dhcp" since the default policy is dhcp already.
We can fix it by following the rule to starting the Ip4 auto configuration.

Cc: Ye Ting <ting.ye@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
Reviwed-by: Ye Ting <ting.ye@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18244 6f19259b-4bc3-4df7-8a09-765794883524
1 file changed